474 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.53. 



Another group referred to Opalia by Carpenter has been separated 

 by De Boury in 1889 under the name of Nodiscala. These are small, 

 slender imperforate shells with ill-defined axial nodes or ribs, but only 

 one true varix, which is terminal and much thickened. The shells 

 when in good condition have a soft calcareous outer coat which is 

 punctate or minutely sculptured, recalling the outer coat in Chlamys. 

 Four species of this group have been described from the coast, E. 

 mazailaniciim Dall, 1908; E. retiporosum Carpenter, 1864, ranging 

 from Catalina Island to the Gulf of California; E. spongiosum, Car- 

 penter, 1864, from Monterey, California; and E. mezicanum Dall, 1908, 

 from Acapulco. 



A very distinct group of boreal forms is Acirsa Morch, 1857 (Aixisa 

 Nyst, 1873), founded on Scalaria horealis Beck, 1839 (not of Gould, 

 1852), of which S. eschrichtii (Holboll) Moller, 1842, and S. ochotcnsis 

 Middendorff, 1849, are synonyms. This species is circumboreal, the 

 more southern specimens are more delicate and smaller than those 

 from truly arctic waters, which at most form a variety which will 

 take Middendorff 's name. On the .Pacific side this species ranges 

 from Bering Straits through Bering and the Okhotsk Seas to the 

 Aleutian Islands. 



Curiously enough a minute form has been received from Cape San 

 Lucas which appears to bt;long to this group, and if so was probably 

 washed up from deep water. The shell is littoriniform, acute, ■with 

 seven whorls, including the somewhat styliform smooth nucleus; 

 the sutures are appressed, the whorls only moderately convex, with 

 very faint axial indications of ribbing, and sharp uniform spiral 

 striation. A prominent thread upon which the suture is laid marks 

 the periphery. The terminal varix is inconspicuous, the margin of 

 the aperture being thickened inside with little outside expansion. 

 Length, 3.6; diameter, 2 mm. U. S. Nat. Mus. Cat. No. 74020. This 

 may take the name of A. exopleura. 



A slender white spirally sulcate shell from the Gulf of California, 

 described by Carpenter as Acirsa menestJioides in 1864, may perhaps 

 be referred to the genus CoutliouyeUa Bartsch, 1909, but its proper 

 place awaits for determination specimens containing the operculum 

 and soft parts. 



Ferminoscala Dall, 1908, contains large yeUow or brown species 

 with finely reticulated surface, large basal disk, and a thick heavy 

 terminal varix. Before the varix is formed the shell has much the 

 aspect of Amaea magnijica Sowerby. E. ferminianum Dall, 1908, 

 ranges from Point Fermin in the Gulf of California to Panama. 

 E. hrunneopictum DaU, 1908, was dredged off Cerros Island, Lower 

 California. E. pompJiolyx Dall, 1889, ranges from Cape San Lucas to 

 the Galapagos Islands, in deep water. 



